18,854 research outputs found
Surface code implementation of block code state distillation
State distillation is the process of taking a number of imperfect copies of a
particular quantum state and producing fewer better copies. Until recently, the
lowest overhead method of distilling states |A>=(|0>+e^{i\pi/4}|1>)/\sqrt{2}
produced a single improved |A> state given 15 input copies. New block code
state distillation methods can produce k improved |A> states given 3k+8 input
copies, potentially significantly reducing the overhead associated with state
distillation. We construct an explicit surface code implementation of block
code state distillation and quantitatively compare the overhead of this
approach to the old. We find that, using the best available techniques, for
parameters of practical interest, block code state distillation does not always
lead to lower overhead, and, when it does, the overhead reduction is typically
less than a factor of three.Comment: 26 pages, 28 figure
Magic-State Functional Units: Mapping and Scheduling Multi-Level Distillation Circuits for Fault-Tolerant Quantum Architectures
Quantum computers have recently made great strides and are on a long-term
path towards useful fault-tolerant computation. A dominant overhead in
fault-tolerant quantum computation is the production of high-fidelity encoded
qubits, called magic states, which enable reliable error-corrected computation.
We present the first detailed designs of hardware functional units that
implement space-time optimized magic-state factories for surface code
error-corrected machines. Interactions among distant qubits require surface
code braids (physical pathways on chip) which must be routed. Magic-state
factories are circuits comprised of a complex set of braids that is more
difficult to route than quantum circuits considered in previous work [1]. This
paper explores the impact of scheduling techniques, such as gate reordering and
qubit renaming, and we propose two novel mapping techniques: braid repulsion
and dipole moment braid rotation. We combine these techniques with graph
partitioning and community detection algorithms, and further introduce a
stitching algorithm for mapping subgraphs onto a physical machine. Our results
show a factor of 5.64 reduction in space-time volume compared to the best-known
previous designs for magic-state factories.Comment: 13 pages, 10 figure
Methodology for bus layout for topological quantum error correcting codes
Most quantum computing architectures can be realized as two-dimensional
lattices of qubits that interact with each other. We take transmon qubits and
transmission line resonators as promising candidates for qubits and couplers;
we use them as basic building elements of a quantum code. We then propose a
simple framework to determine the optimal experimental layout to realize
quantum codes. We show that this engineering optimization problem can be
reduced to the solution of standard binary linear programs. While solving such
programs is a NP-hard problem, we propose a way to find scalable optimal
architectures that require solving the linear program for a restricted number
of qubits and couplers. We apply our methods to two celebrated quantum codes,
namely the surface code and the Fibonacci code.Comment: 11 pages, 12 figure
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